Electron tube



F. SCHRC JTER Few-5., 15, was

ELECTRON TUBE Filed July 14, 1934 INVENTOR FRITZ SCH/ZOTER 7%. ZWW

ATTORNEY Patented Feb. 15, 1938 UNITED STATES PATENT OFFICE ELECTRON TUBE tion of Germany Application July 14, 1934, Serial No. 735,203 In Germany July 28, 1933 Claims.

In gas contained Braun tubes serving as television scanning means or as television picture receiver, the so-called ion cross caused by the neutral zone of the electrostatical deviation fields 5 (zero point anomaly) causes disturbance. For

on the one hand, the ion space charge effect produces a field distortion between the deviation plates which reduces the deviation velocity of the electron ray in the zero zone, thus also causing a distortion of the picture. In addition, the slower movement of the electron ray produces on the receiving screen an increased brilliancy discernible as a brighter cross standing out from the background. 15 The invention has for its purpose to avoid this disturbing phenomenon. It consists in the compensation of the space charge produced in the zero zone by the positive ions, by a correspondingly apportioned space charge of negative gas or vapor ions. In accordance therewith electronegative gases or vapors, for instance iodine vapor or vapor of metallic or non-metallic halogen compounds are provided in the Braun tube. The heavy negative ions which may then be produced in a small amount by adhesion of electrons onto the gas or vapor particles, and which due to their inertia of the mass have approximately the same electrical movability as the positive ions remain mixed with the latter and compensate the otherwise forming disturbing space charge 3 eiiect. In carrying out the invention it is of advantage to employ in the tube such compounds of electro-negative elements which at a definite temperature, for instance in the vicinity of the heated cathode, begin to dissociate, such as zircon chloride, thallithallo-chlo-ride and the like. In selecting the respective substance not only must its capability of producing suitable vapors at the desired pressure be considered, but also its chemical behaviour with respect to metallic electrodes of the tube and in particular with respect to the cathode whose function during the entire duration of action should be influenced as little as possible. 45 In the drawing I have shown schematically one embodiment of my invention.

Referring to the drawing, the envelope 1 has mounted within it the thermionic cathode 3 and the focusing cathode 5. Positioned adjacent to the cathode is a heat dissociable halogen compound so that upon the heating of the thermionic cathode, the compound dissociates to produce electron negative ions. 5

Besides the electro-negative gases or vapors which are required in an extremely low concentration only, the inert filling gases such as argon, neon or helium ordinarily used in Braun tubes are suitably present, they are even necessary un- 10 der certain circumstances, since without their presence the desired concentration action holding the electron ray together, would be absent.

Having thus described the invention, what I claim is:

1. In a cathode ray tube wherein is provided a cathode, the method of supplying an electronegative vapor comprising the steps of positioning a heat-dissociable halogen compound adjacent to the cathode and supplying heat to said cathode to produce dissociation of said compound.

2. In a cathode ray tube wherein is provided a cathode, the method of supplying an electronegative vapor comprising the steps of positioning zircon chloride adjacent to the cathode and supplying heat to said cathode to produce dissociation of said compound.

3. In a cathode ray tube wherein is provided a cathode; the method of supply electro-negative vapor comprising the steps of positioning thallithallo chloride adjacent to the cathode, and supplying heat to said cathode to produce dissociation of the compound.

4. An electron device comprising a glass envelope, a thermionic cathode within said envelope for emitting electrons, electron focusing means cooperating with said cathode, and a heat dissociable halogen compound adjacent to said cathode.

5. An electron device comprising a glass envelope, a thermionic cathode within said envelope for emitting electrons, electron focusing means cooperating with said cathode, a heat dissociable halogen compound adjacent to said cathode, and a gas chosen from Group VIII of the Periodic Series under low pressure filling said envelope.

FRITZ scHRc'iTER. 

